How easy is it to change network domain to 'fool' GA?

Hi, I just got an extensive and a thorough visit on my business's website by a what appeared to be a 'government agency'. I have no reason to believe why they would look up my business or browse my website.

The network domain they were using ends with a .gov and I am not sure if it indeed is that government agency or somebody 'pretending' to be them. I do have ex girlfriend who constantly browses my website. I do want to disclose the name of that federal agency but you might have gotten some idea by now. So my question is 'how easily could one alter their network domain and service providers' name to fool GA'..?